Transmitter



Feb. 6, 1940. H, E- HOLLMANN 2,189,584

TRANSMITTER Filed June 18, 1957 M/C'RPHUNE I AMPM/ER INVENTOR HANS ERICH HozLMAN/v BY MWW ATTORNEY Patented Feb. 6, 1940 TRANSMITTER Hans Erich Hollmann, Berlin, Germany, assigner to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H.,'Berlin, Germany, a corporation of Germany In Germany July 22, 1936 Application June 1s, 1937, serial No. 148,861

13 Claims.

The invention relates to an arrangement for controlling the transmission of ultra-short wave high-frequency energy passing from a generator to a load,` more especially to an antenna across 5 a concentric tubular line.

When modulating an ultra-short wave transmitter, it is known that the necessary condition of operating outside the so-called disruption region can only be fullled under difliculties. Ow-

m ing partly to the instability of the resonant circuits, and partly to the fact that the electrons have only a nite velocity, the conditions for building up a satisfactory modulating system for application to ultra-short waves, are no longer m as simple asin the case of longer waves. It is very dilcult, therefore, to modulate the transmitter proper by influencing its operating conditions. Furthermore, in using ultra-short waves, it should also be borne in mind that the zo excited transmitter wavedepends to a greater or lesser degree on the operating state of the transmitter so that if the feed potentials are varied, the desired amplitude modulation is accompanied in a greater or lesser degree by an.

u undesired frequency modulation.

In vorder to avoid these diiiiculties, various methods have hitherto been proposed aiming at a control of the high-frequency energy outside the actual generator and independent of the conditions of excitation of .the transmitter oscillations. Thus, the energy already radiated can, y after having left the antenna, be subsequently modulated, for instance, by causing the waves to pass through a layer of ionized gas whose u degree of ionization isV varied in the rhythm of the modulation, and which thus permits at one time the passage of a greater amount of radiation energy and at another time a smaller amount, or absorbs this amount of energy. Since the size of the gaseous layer is to be large as compared with the wave length, this method can be employed only for extremely short waves. It appears, therefore, to be a better and simpler method to catch the high-frequency oscillations on their way from the oscillation generator to u the antenna, namely in the antenna feed line. To

this end, variable high-frequency resistors which can be influenced to a large extent in a manner free of inertia, are inserted in the transmission line and which block the passage of the highfrequency energy passing from the generator to the antenna, or render such passage diilicult, or permit the passage at an optimum eciency. For such variable resistances, glow tubes are found 'u to be well suited, since the amplitude of the (ci. 25o- 17) electron discharge therein. may be controlled in the rhythm of the modulation to be impressed upon the transmitter oscillations. If such a glow tube is placed between the Vtwo wires of a Lecher A system, the ionized gas exerts a detuning action, 5

as well as an energy absorbing action upon the Lecher line, thus inuencing amplitude of the oscillations radiated by the antenna, in accordance with the varying conditions of ionized gas.

The hithertoknownpractical embodiments of lo this method are such that a glow discharge tube of elongated shape, for instance of the type employed in oscillographs, is placed directly between the two Lecher wires extending from transmitter to the antenna, at which place it acts in' part as capacitive lateral resistance between the Lecher wires with a dielectric fluctuating in its special extent, as well as in its density in the rhythm of the modulation, and acting on the other hand as an energy consuming, and as a variable damping resistance. In order to exploit as much as possible the detuning, and damping action of the ionized gas, it is advisable in addition to using solely the Lecher wires as layers for the gaseous condenser, to enlarge the surface of said gas by means of special metallic layers in contactwith the Lecher wires. These layers on the other hand entail the disadvantage that they increase the residual capacity which prevails when the glow tube is not ignited. As a result thereof, the optimum transmission of energy to the antenna will be disturbed, andthe upper limit of the control range will be decreased. In practice therefore, a compromise must be made between the two required conditions one of which is' to employ the largest possible condenser layers, and the other of which is to obtain the lowest possible initial capacity. Such a compromise, however, is opposed to the operation of the transmitter at highest efficiency.

The present invention overcomes eiectively this drawback in that for the transmission of energy from the generator to the load, such as an antenna for instance, a concentric tubular line known as such is'used within which the glow tube Ais so arranged that a concentric glow discharge will be formed between the inner tube and the outer tube. Hence, the entire glow discharge participates in the control of the transmission of energy to the antenna, without the presence of special metal surfaces whereby the capacity per unit length of the line would be varied. Consequently, the eiiiciency of the transmission will conductor of said device forming an anode for said device and being arranged in the same straight line as the outer conductors of said two sections of concentric line.

6. A system in accordance with claim 1, characterized in this, that the impedance of said concentric line is matched at its ends to the impedances of said source and utilization circuit. v'7. A concentric transmission line having an inner and an outer conductor, a source of high frequency oscillations connected to one end of said line, a utilization device connected to the other end of said line, an electron discharge tube certain electrodes of which are concentric to each other and constitute portions of said transmission line, and means for modulating said high frequency oscillations, said means being operable to vary the impedance of the discharge path in said discharge tube.

8. A concentric transmission line having an inner and an outer conductor, a source of high frequency oscillations connected to one end of said line, a utilization device connected to the other end of said line, a gaseous electron discharge tube certain electrodes of which are concentric to each other and constitute portions of said transmission line, and means for modulating said high frequency oscillations, said means being operable to vary the impedance of the discharge path in said discharge tube.

9. A system in accordance with claim 7 and further characterized in that said electron discharge tube possesses a centrally disposed linear cathode connected to and between different portions of the inner transmission line conductor.

`and an outer electrode connected to and between different portions of the outer transmission line conductor.

10. A transmission line having coaxial inner and outer conductors, a source of high frequency oscillations connected to one end of said line, a utilization device connected to the other end of said line, an electron discharge tube forming a connecting link between two portions of said line, said tube containing an anode two terminals of which are respectively connected to diiferent portions of said outer conductor, and a cathode two terminals of which are respectively connected to different portions of said inner conductor, and means connected to said anode and cathode through said conductors for varying the impedance of said tube.

11. A transmission line having coaxial inner and outer conductors, a resonant circuit comprising a loop of conductor interconnecting two adjacent ends of the inner and outer conductors respectively, a source of ultra-high frequency oscillations coupled to said resonant circuit, an electron discharge device having at least one electrode which constitutes an interconnecting link between diierent portions of said line, and means including a connection through one of said conductors for activating said device.

12. Apparatus in accordance with claim 11 and having means for varying the impedance of said electron discharge device, said means serving also to modulate the ultra high frequency energy impressed on said transmission line.

v13. A transmission line having coaxial inner and outer conductors, a gaseous discharge tube having an outer electrode which forms an interconnecting link: between diiferent portions of said outer conductor, said tube also having a linear cathode which forms an interconnecting link between different portions of said inner conductor, a resonant circuit having a capacitor intercoupling dilerent portions of an inductive loop, said loop portions being connected respectively to the inner and outer conductors, and means for producing a glow discharge in said tube, said means having connections across the terminals of said capacitor.

HANS ERICH HOLLMANN. 

